Issue with mission

While in game the mission that im doing i have to kill the magical Skeletons and I can't see the enemy. While on my friends screen I can see the enemy hitting, But on my screen I cant see them at all but im still taking damage and I dont see a name. ALso because of this issue my game keeps on crashing. Before i got to the story quest " Skeletons in my deepcroft" my game was running smoothly. Now my game crashes every second http://https://www.flickr.com/photos/140721233@N05/shares/8N8dh5